Circuits to control and drive motors, such as brushless DC (BLDC) motors, are known. Some motor driver circuits control the motor speed by providing a variable motor supply voltage that is generated by a variable motor supply voltage circuit based in part on a motor feedback signal. This speed control scheme has the advantage of not requiring a dedicated motor speed control input to the driver circuit, since the only connections required are the supply voltage, ground, and feedback signal connections. However, the motor speed range and efficiency can suffer with this three-wire scheme.
Alternatively, some motor driver circuits respond to an external speed control signal, such as a Pulse Width Modulation (PWM) signal. While this type of motor driver circuit can provide an extended speed range for the motor, an additional connection is required to accommodate the speed control signal.